Heiko Bleher sheds some light on the Paracheirodon genus, which currently contains several species including the Neon tetra, Cardinal tetra and Green neon tetra.

Three species of tetra from the Neon and Cardinal tetra genus are scientifically described and one is awaiting description. I discovered the latter in 2006 for the first time and it was the first Paracheirodon found south of the Amazon.

Paracheirodon n. sp. is so far known only from a single creek in the Purus river basin, south of the Amazon. It is genetically more distant from the Neon tetra (P. innesi) than the Cardinal (P. axelrodi) and from the Green neon (P. simulans, shown above). It’s unlikely to ever appear in the hobby as a wild-caught fish as it is too far away from civilisation.

The Neon tetra (Paracheirodon innesi, Myers, 1936) is only known from the western Amazon, Peru and parts of western Amazon state in Brazil — and the world’s most widely bred aquarium fish. Rarely do wild-caught specimens of this species reach the hobby.

The Cardinal tetra (Paracheirodon axelrodi, Schultz, 1956) is found only in the Rio Negro basin up to its source in Colombia. It is one of the most popular aquarium fish. Although most hobby specimens are still wild caught, many are now being bred worldwide, particularly in eastern Europe.

The Green neon tetra, (Paracheirodon simulans, Géry, 1963), species finds its distribution also restricted to the Rio Negro basin and is frequently found with the Cardinal tetra (P. axelrodi).

It is the smallest of the four species and the only one with the neon stripe from mouth to tail. P. simulans has hardly been bred in captivity, most specimens in the hobby being from the wild.

This item was first published in the September 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.